fix(shell-api): map fields to projection in findAndModify MONGOSH-1820 (#2100)

Author: addaleax

packages/shell-api/src/collection.spec.ts

@@ -1798,11 +1798,12 @@ describe('Collection', function () {
           ...options,
         });
 
+        const { fields: projection, ...expectedOptions } = options;
         expect(serviceProvider.findOneAndDelete).to.have.been.calledWith(
           collection._database._name,
           collection._name,
           { query: 1 },
-          { ...options, sort: { sort: 1 } }
+          { ...expectedOptions, sort: { sort: 1 }, projection }
         );
       });
     });

packages/shell-api/src/collection.ts

@@ -482,8 +482,19 @@ export default class Collection extends ShellApiWithMongoClass {
       FindAndModifyMethodShellOptions,
       'query' | 'update'
     > = { ...options };
+    if (
+      reducedOptions.projection !== undefined &&
+      reducedOptions.fields !== undefined
+    ) {
+      throw new MongoshInvalidInputError(
+        'Cannot specify both .fields and .projection for findAndModify()',
+        CommonErrors.InvalidArgument
+      );
+    }
+    reducedOptions.projection ??= reducedOptions.fields;
     delete (reducedOptions as any).query;
     delete (reducedOptions as any).update;
+    delete (reducedOptions as any).fields;
     if (options.remove) {
       return this.findOneAndDelete(options.query, reducedOptions);
     }

packages/shell-api/src/helpers.ts

@@ -783,6 +783,7 @@ export type FindAndModifyMethodShellOptions = {
   remove?: boolean;
   new?: boolean;
   fields?: Document;
+  projection?: Document;
   upsert?: boolean;
   bypassDocumentValidation?: boolean;
   writeConcern?: Document;

packages/shell-api/src/integration.spec.ts

@@ -1097,6 +1097,24 @@ describe('Shell API (integration)', function () {
         });
       });
 
+      it('projects according to `fields`', async function () {
+        const result = await collection.findAndModify({
+          query: { doc: 4 },
+          new: true,
+          update: { doc: 4, asdf: true },
+          upsert: true,
+          fields: { asdf: 1, _id: 1 },
+        });
+        expect(Object.keys(result!)).to.deep.equal(['_id', 'asdf']);
+        expect(result!._id.constructor.name).to.equal('ObjectId');
+        expect(result!.asdf).to.equal(true);
+
+        expect(await findAllWithoutId(dbName, collectionName)).to.deep.include({
+          doc: 4,
+          asdf: true,
+        });
+      });
+
       context('on server 4.2+', function () {
         skipIfServerVersion(testServer, '< 4.2');
         it('allows update pipelines', async function () {